Stuart Kennedy

A Family of Calix{[}4]arene-Supported {[}(Mn2Mn2II)-Mn-III] Clusters

In the cone conformation calix[4]arenes possess lower-rim polyphenolic pockets that are ideal for the complexation of various transition-metal centres. Reaction of these molecules with manganese salts in the presence of an appropriate base (and in some cases co-ligand) results in the formation of a family of calixarene-supported [Mn(III)(2)Mn(II)(2)] clusters that behave as single-molecule magnets (SMMs). Variation in the alkyl groups present at the upper-rim of the cone allows for the expression of a degree of control over the self-assembly of these SMM building blocks, whilst retaining the general magnetic properties. The presence of various different ligands around the periphery of the magnetic core has some effect over the extended self-assembly of these SMMs.

Calixarene supported enneanuclear Cu(II) clusters

New pseudo-trigonal planar supramolecular building blocks housing tri-capped trigonal prismatic [Cu(9)] clusters have been isolated from the facile reaction of Cu(II) salts with p-(t)But-calix[4]arene.

Fluorescent carbon quantum dot hydrogels for direct determination of silver ions

The paper reports for the first time the direct determination of silver ion (Ag(+)) using luminescent Carbon Quantum Dot hydrogels (CQDGs). Carbon Quantum Dots (CQDs) with different superficial moieties (passivate-CQDs with carboxylic groups, thiol-CQDs and amine-CQDs) were used to prepare hybrid gels using a low molecular weight hydrogelator (LMWG). The use of the gels results in considerable fluorescence enhancement and also markedly influences selectivity. The most selective CQDG system for Ag(+) ion detection proved to be those containing carboxylic groups onto their surface. The selectivity towards Ag(+) ions is possibly due to its flexible coordination sphere compared with other metal ions. This fluorescent sensing platform is based on the strong Ag-O interaction which can quench the photoluminescence of passivate-CQDs (p-CQDs) through charge transfer. The limit of detection (LOD) and quantification (LOQ) of the proposed method were 0.55 and 1.83µgmL(-1), respectively, being applied in river water samples.

Modulation of nanotube packing through the controlled self-assembly of tris-p-carboxylatocalix[4]arenes

Crystallisation of tris-carboxylatocalix[4]arenes from pyridine affords self-assembled layered and triply helical nanotubular arrays; the latter of these represents a modulation of nanotubule spacing in a persistent self-assembly motif.

Calixarene nanotubes: structural tolerance towards pyridine templates

Crystallisation of a tris-p-carboxylatocalix[4]arene from various pyridine derivatives leads, in some cases, to further self-assembly into triply helical nanotubes, demonstrating the degree of tolerance of the structure motif towards the introduction of alkyl groups around the aromatic ring of the guest template.

Structural alteration of the metal–organic pyrogallol[4]arene nano-capsule motif by incorporation of large metal centres

Addition of cadmium(II) nitrate to gallium-coordinated metal-organic C-alkylpyrogallol[4]arene nano-capsules affords a variation of the near spherical hexamer motif, structural changes in which are induced by the markedly different nature of the secondary incorporated metal.

Salt formation affects the conformational and assembly properties of p -carboxylatocalix[4]arenes

The conformational properties and self-assembly behaviour of the p-carboxylatocalix[4]arenes, when in the presence of a pyridine template, are well understood. Salt formation with these molecules, a process driven by the introduction of an amino group to the 2-position of the pyridine template, has dramatic consequences on both building block conformation and the resulting self-assembly.

Eliminating disorder in a self-assembled calixarene nanotube

Synthesis of a previously unobtainable calixarene building block eliminates disorder both within and between template-assembled nanotubes. This allows for elucidation of the role of all co-crystallised components and observation of the key intermolecular interactions in the resulting system.

Tailored supramolecular gel and microemulsion crystallization strategies – is isoniazid really monomorphic?

We report the application of supramolecular gel and microemulsion droplet crystallisation methodologies to isoniazid crystallization. Tailored gelators have been designed with isoniazid mimetic functionality in an attempt to control crystal morphology and polymorphic behaviour. Microemulsion crystallisation was investigated to achieve thermodynamic control over drug crystallisation. Both techniques resulted in only a single form of isoniazid implying that it is genuinely monomorphic.